Donald Kirkendall, an exercise physiologist at the University of North Carolina, will never forget the time he put a heart-rate monitor on a member of the United States rowing team and asked the man to row as hard as he could for six minutes.

The standard formula for calculating how fast a human heart can beat calls for subtracting the person’s age from 220. The rower was in his mid- 20’s.

Just getting the heart to its actual maximum rate is an immense effort and holding it there for even a minute is so painful that it is all but inconceivable for anyone who is not supremely motivated, Dr. Kirkendall said. But this rower confounded the predictions.

“His pulse rate hit 200 at 90 seconds into the test,” Dr. Kirkendall said. “And he held it there for the rest of the test.” A local cardiologist was looking on in astonishment and told Dr. Kirkendall, “You know, there’s not a textbook in the world that says a person could have done that.”

“I’ve kind of laughed about it over the years,” Dr. Haskell said. The formula, he said, “was never supposed to be an absolute guide to rule people’s training.” But, he said, “It’s so typical of Americans to take an idea and extend it beyond what it was originally intended for.”